1. Field of the invention
The present invention is directed to an inflator, or gas generator, which is suitable for use with vehicle airbag passive restraint systems. More particularly, this invention is directed to an improvement to inflators which generate gas, at least in part, by the reaction of a fluid fuel with an oxidizing agent.
2. Description of background and related art
Airbag passive restraint systems are now provided in virtually all of the automobiles presently being manufactured in this country. These systems rely on a crash sensing device initiating the operation of an inflator causing the rapid release or generation of a quantity of gas which rapidly inflates a cushion, or airbag, causing it to deploy to a position between a vehicle occupant and hard surfaces on the vehicle into which the occupant might otherwise be propelled. Various inflators have been used. Originally they relied on the rapid release of a quantity of a compressed gas. Later inflators relied on the rapid generation of gas by the reaction of solid gas generating materials, such as sodium azide, with an oxidizing agent to produce the inflation gas. So called hybrid inflators relied on the exothermic oxidizing reaction of solid gas generating materials to produce a generated gas and heat, which was then mixed with a compressed inert gas as it is released from storage heating it to an increased temperature whereby the mixed gas exhibits an enhanced volume/pressure relative to what it would have exhibited were its temperature not increased. Recently, a new type of inflator has been introduced which relies on the combustion of a fluid fuel to generate a volume of heated gas, which can be used as the inflation gas directly, or, similar to the hybrid inflators, can be used to mix with and heat a compressed inert gas as it is released to the airbag.
Several examples of the new fluid fuel inflators can be found in U.S. Pat. Nos. 5,060,973 to Giovanetti, 5,330,730 to Brede et al., 5,350,192 to Blumenthal, 5,470,104 to Smith et al., 5,487,561 to Mandzy et al., 5,494,312 to Rink, 5,529,333 to Rizzi et al. and 5,531,473 to Rink. Some of these new fluid fueled inflators store a mixture of the fluid fuel with an oxidizing gas, while others store the fluid fuel and oxidizing agent separately, only bringing them together when the inflator is activated. Some of the fluid fuel inflators provide the fuel as a liquid while others provide it as a gas.
The present invention relates to fluid fuel inflators wherein the fuel is stored as a liquid and is stored separate from the oxidizing agent. In such inflators, the liquid fuel is provided in a separate storage chamber. Typically such storage chambers have comprised a fuel bottle mounted to an adapter so as to be located adjacent to, or partially about, an initiator device such as a squib. Typically these components are assembled by, first, filling the bottle with the liquid fuel, separately assembling the initiator to the adapter, providing an O-ring, slipping the fuel bottle either over or into the adapter and applying a laser weld where the bottle adjoins the adapter. While these assemblies usually perform satisfactorily, we have found that occasionally the desired leak proof seal is not achieved, allowing fuel to leak out of the fuel bottle. We have also found that sometimes the fuel bottle separates from the adapter during airbag deployment. It is generally undesirable to permit any solid parts to be loose during the fuel combustion/gas generation operations which occur during deployment since such parts could become flying projectiles, and/or block or restrict orifices within the inflator causing erratic and possibly unsatisfactory performance by the assembly.